1. Field of the Invention
This invention relates to railroad cars and more particularly to side bearing units attached to a bolster of each truck of the car to regulate independent movement of a body of the car and impede truck hunting associated with higher speed travel.
2. Prior Art
For some time, side bearing units have been used to regulate relative movement between a body of a railroad car and trucks carrying ends of the car body respectively. One such side bearing unit is disclosed in U.S. Pat. No. 3,712,691 and includes a housing containing a pair of resilient cushions. The resilient cushions in turn support a cap member having a downward contoured projection which in part fits between the cushions. A top wall of the cap frictionally engages a bearing member attached to a bottom of the railroad car body.
A more recent railroad vehicle side bearing unit is disclosed in U.S. Pat. No. 3,910,655. This unit includes a housing containing a block of resilient material formed with an upper V-shaped groove. A cap fits over the block and has a central projection which fits into the groove and radiused inner facing sidewalls. When the cap is compressed by the weight of the car body, deformation of the block is in part restricted by the cap sidewalls.
A still further side bearing unit is set forth in U.S. Pat. No. 4,080,016. This unit includes a base with a housing formed by upright sidewalls and connecting end portions. Within the housing are a pair of elastomeric blocks spaced apart by a saddle block. An upper surface of the saddle block has a cusp to separate a pair of roller bearings. Each elastomeric block is formed with a relatively soft lower portion and stiff upper portion having a top surface to engage a wear plate afixed to the body of the railroad car. A fully loaded car body compresses the elastomeric blocks sufficiently so that the wear plate engages the roller bearings. This engagement reduces frictional restraints to relative movement between the bearing unit and car body.